gettext.sh: fixup calls to absolute paths

For discussion see https://github.com/NixOS/nixpkgs/pull/13072

pkgs/development/libraries/gettext/absolute-paths.diff

@@ -0,0 +1,21 @@
+diff --git a/gettext-runtime/src/gettext.sh.in b/gettext-runtime/src/gettext.sh.in
+index 1dfa3bb..d6ef8a8 100644
+--- a/gettext-runtime/src/gettext.sh.in
++++ b/gettext-runtime/src/gettext.sh.in
+@@ -86,14 +86,14 @@ fi
+ # looks up the translation of MSGID and substitutes shell variables in the
+ # result.
+ eval_gettext () {
+-  gettext "$1" | (export PATH `envsubst --variables "$1"`; envsubst "$1")
++  @out@/bin/gettext "$1" | (export PATH `envsubst --variables "$1"`; envsubst "$1")
+ }
+ 
+ # eval_ngettext MSGID MSGID-PLURAL COUNT
+ # looks up the translation of MSGID / MSGID-PLURAL for COUNT and substitutes
+ # shell variables in the result.
+ eval_ngettext () {
+-  ngettext "$1" "$2" "$3" | (export PATH `envsubst --variables "$1 $2"`; envsubst "$1 $2")
++  @out@/bin/ngettext "$1" "$2" "$3" | (export PATH `envsubst --variables "$1 $2"`; envsubst "$1 $2")
+ }
+ 
+ # Note: This use of envsubst is much safer than using the shell built-in 'eval'

pkgs/development/libraries/gettext/default.nix

@@ -7,6 +7,7 @@ stdenv.mkDerivation (rec {
     url = "mirror://gnu/gettext/${name}.tar.gz";
     sha256 = "0pb9vp4ifymvdmc31ks3xxcnfqgzj8shll39czmk8c1splclqjzd";
   };
+  patches = [ ./absolute-paths.diff ];
 
   outputs = [ "out" "doc" ];
 
@@ -28,7 +29,8 @@ stdenv.mkDerivation (rec {
         "gt_cv_func_CFLocaleCopyCurrent=no"
       ]);
 
-  patchPhase = ''
+  postPatch = ''
+   substituteAllInPlace gettext-runtime/src/gettext.sh.in
    substituteInPlace gettext-tools/projects/KDE/trigger --replace "/bin/pwd" pwd
    substituteInPlace gettext-tools/projects/GNOME/trigger --replace "/bin/pwd" pwd
    substituteInPlace gettext-tools/src/project-id --replace "/bin/pwd" pwd